Certain diesel engines have fuel injection systems that utilize hydraulic fluid (oil) under pressure to force fuel into engine combustion chambers. The hydraulic fluid is supplied to a respective fuel injector at each engine cylinder. When a valve mechanism of a fuel injector is operated by an electric signal from an engine control system to inject fuel into the respective cylinder, the hydraulic fluid is allowed to act on a piston in the fuel injector to force a charge of fuel into the respective combustion chamber.
A fuel injection control strategy may include a strategy for controlling the pressure of the hydraulic fluid that is supplied to the fuel injectors. The pressure may vary depending on the values of certain input data utilized in the control strategy. One type of hydraulic system for controlling the pressure comprises a regulator valve that is controlled by the engine control system's execution of the pressure control strategy. If a fuel injector comprises an intensifier piston that forces the ejection of fuel from the injector, the pressure applied to the fuel will be some multiple of the hydraulic pressure applied by the hydraulic system to the fuel injector.
The pressure control strategy may utilize closed-loop control that seeks to secure correspondence of actual pressure to a desired control pressure. However, to enhance performance, the control strategy may include a feed-forward component that improves response to changing inputs that influence control pressure.
Other types of fuel injection systems regulate the injection pressure directly at a fuel rail or fuel manifold that serves the injectors that are connected to it.